Page:HouseSparrowHomeAbroad.djvu/18

10 The low insertion of the hind toe and its length; its great power of opposibility to the front toes; and the superior mobility of the same, which is secured by the separation of its principal muscle from that which Hexes the other toes collectively, perfectly adapt the feet for grasping. The hind toe is always present, and is never directed anteriorly, or laterally. The feet are never zygodactyly esy ndactyle, nor semipal mate, although the anterior toes, for a part or the entire length of the basal joints, are usually immovably joined to each other. For further particulars, the reader should examine some standard work upon classification.

The species belonging to this order are the typical Insessores, and represent the highest grade of development, as well as the most complex of the class. They possess high physical irritability, the result of a rapid respiration and circulation; of all birds, they consume the most oxygen, and live the fastest.

The Passeres comprise the great majority of birds. They are separated into two groups, ordinarily designated suborders, from the structure of the inferior larynx. In one, this organ is a complicated muscular vocal apparatus; while in the other, it is less developed, rudimentary, or lacking.

The above constitutes the higher of the two suborders previously referred to; comprising species, which possess a more or less complicated vocal apparatus, consisting of five sets of muscles; but many of them are unable to